DE SOTO -- Spotted bass have invaded the Big River, and smallmouth bass may be paying the price, according to Kevin Meneau, fisheries management biologist with the Missouri Department of Conservation (MDC). But hard times for smallmouths could spell good times for anglers who want to put more fish in the frypan.

Meneau said that during the mid-1970s, spotted bass migrated into the lower Big River via the Meramec River. Apparently they found things to their liking. Within 10 years spotted bass outnumbered largemouth and smallmouth bass combined. Between 1987 and 1990, spotted bass moved 50 miles up Big River, almost to Highway 21.

At the same time, anglers reported a decrease in the number of smallmouths they were catching. Meneau is concerned that the non- native spotted bass may be out-competing smallmouths for available food.

He also worries because spotted bass (sometimes called Kentucky bass) are known to spawn with smallmouths and produce hybrids. This may reduce the spawning success of smallmouths.

"The Big River is one of the streams where we have established smallmouth bass special management areas to build a high-quality smallmouth bass fishery," said Meneau. "We want to ensure that the smallmouth remains the dominant black bass there."

To that end, biologists are testing a strategy that has never been tried in Missouri. MDC has eliminated the length limit on spotted bass from the mouth of the Big River upstream to the Highway 21 bridge near De Soto.

Spotted bass are slow-growing. Most die of natural causes before reaching the old minimum length limit of 12 inches. Consequently, anglers seldom got to harvest spotted bass in the past. Meneau hopes that removing the length limit will encourage anglers to take home more spotted bass, giving smallmouth bass in the Big River a fighting chance.

The daily limit on black bass on the Big River remains unchanged at six in the aggregate. In other words, anglers can take home six spotted bass daily or a combination of spotted, largemouth and smallmouth bass up to six daily.

Remember that only one of the six may be a smallmouth, and it must be 15 inches long to be kept in the Special Smallmouth Bass Management Area from Mammoth Road bridge to Brown's Ford Road bridge. Also remember that black bass season runs from the Saturday before Memorial Day through Feb. 28 south of the Missouri River.

To cash in on the spotted bass bonus, anglers must learn to tell the three black bass species apart. Largemouth and spotted bass have a dark horizontal stripe down the middle of their sides. Smallmouths don't. Instead, their backs and flanks are brownish, often with vertical stripes that have earned them the nickname "tiger bass." Spotted and largemouth bass are greenish in color.

When the mouth of the largemouth bass is closed, the rear corner extends well behind the eye. This is not true of either the spotted or smallmouth bass.

Spotted bass are further distinguished from largemouths by the presence of a rough patch on their tongues. Most largemouth bass lack this tooth patch.

Finally, spotted bass have horizontal rows of dark spots along their lower sides. These spots are absent on largemouths and smallmouths.

These characteristics are outlined on signs posted at access sites on the Big River. You can receive a free black bass identification brochure by writing to: Missouri Department of Conservation, Fisheries Division, "Black Bass," P.O. Box 180, Jefferson City, MO 65102-0180.

"If the new regulation works as planned, Big River anglers will get to eat more spotted bass and improve smallmouth fishing at the same time," said Meneau.

Some bass in the Big River have small, orange spaghetti-like tags near the fins on top of their backs. Meneau asks anglers who catch tagged bass to report their catches. This can be done either by clipping off the tag or by leaving it in place and recording the serial number on it and sending it to any MDC office.

Fisheries managers also need to know when, where and by what method the fish was caught, its length and species and whether it was kept or released. Send this information to: Missouri Department of Conservation, 1110 S. College Ave., Columbia, Mo., 65201-5204.